From: Christian Brauner <brauner@kernel.org>
Date: Fri, 6 Jun 2025 09:45:08 +0000 (+0200)
Subject: netns: use stable inode number for initial mount ns
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9b0240b3ccc325c7a96cf362877180bc9e10d546;p=thirdparty%2Fkernel%2Fstable.git

netns: use stable inode number for initial mount ns

Apart from the network and mount namespace all other namespaces expose a
stable inode number and userspace has been relying on that for a very
long time now. It's very much heavily used API. Align the network
namespace and use a stable inode number from the reserved procfs inode
number space so this is consistent across all namespaces.

Link: https://lore.kernel.org/20250606-work-nsfs-v1-2-b8749c9a8844@kernel.org
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
---

diff --git a/include/linux/proc_ns.h b/include/linux/proc_ns.h
index e77a37b23ca7e..3ff0bd381704b 100644
--- a/include/linux/proc_ns.h
+++ b/include/linux/proc_ns.h
@@ -47,6 +47,7 @@ enum {
 	PROC_PID_INIT_INO	= PID_NS_INIT_INO,
 	PROC_CGROUP_INIT_INO	= CGROUP_NS_INIT_INO,
 	PROC_TIME_INIT_INO	= TIME_NS_INIT_INO,
+	PROC_NET_INIT_INO	= NET_NS_INIT_INO,
 };
 
 #ifdef CONFIG_PROC_FS
diff --git a/include/uapi/linux/nsfs.h b/include/uapi/linux/nsfs.h
index 6683e7ca39960..393778489d85e 100644
--- a/include/uapi/linux/nsfs.h
+++ b/include/uapi/linux/nsfs.h
@@ -49,6 +49,7 @@ enum init_ns_ino {
 	PID_NS_INIT_INO		= 0xEFFFFFFCU,
 	CGROUP_NS_INIT_INO	= 0xEFFFFFFBU,
 	TIME_NS_INIT_INO	= 0xEFFFFFFAU,
+	NET_NS_INIT_INO		= 0xEFFFFFF9U,
 };
 
 #endif /* __LINUX_NSFS_H */
diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index ae54f26709ca2..03cf87d3b3801 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -796,11 +796,19 @@ static __net_init int net_ns_net_init(struct net *net)
 #ifdef CONFIG_NET_NS
 	net->ns.ops = &netns_operations;
 #endif
+	if (net == &init_net) {
+		net->ns.inum = PROC_NET_INIT_INO;
+		return 0;
+	}
 	return ns_alloc_inum(&net->ns);
 }
 
 static __net_exit void net_ns_net_exit(struct net *net)
 {
+	/*
+	 * Initial network namespace doesn't exit so we don't need any
+	 * special checks here.
+	 */
 	ns_free_inum(&net->ns);
 }